Model engine starter



June 26, 1956 P. M. DE GROAT 2,751,898

MODEL ENGINE STARTER Filed Aug. 5, 1954 FIG.|. FIG. 2.

PHILIP M. DE GROAT INVENTOR.

United States Patent G MODEL ENGINE STARTER Philip Miles De Groat, 'Binghamton, N. Y. Application August 3, 1954, Serial No. 447,553

9 Claims. (Cl. 123-179) .Heretofore, however, model engines have been handicapped by the diificulty of getting them started, particularly with propeller driven types, as by flicking the pro- .peller'with the finger. This has proven to be an unsatisfactory and hazardous method in that the engine compression ordinarily precludes the starting stroke from exceeding one engine cycle, which ordinarily is inadequate, and injuries commonly occur when the propeller strikes the back of the finger, once the engine starts. While self-starting devices have been used on larger engines, their weight and cost have precluded them from successful use with model engines, particularly in airborne applications.

A principal object of the present invention, therefore, is to provide a new and improved type of self-starting mechanism adapted for use with model internal-combustion engines; another object is to provide such a starter of such light weight that it will not materially detract from the performance of a model aircraft to which it is applied; to provide an improved starter that is readily mounted onor de-mounted from a model internal-combustion engine; and to provide a model engine with starting mechanism in such exposed position that it can readily be operated and serviced. These and other objects of the invention will become more apparent from the following description, and from the appended drawings, showing one form of the invention as applied to a popular type of miniature engine.

In the drawing- Fig. l is a side view of a propeller-driven engine, showing one form of the improved starter in neutral or disengaged position;

Fig. 2 is a front view of the same engine showing the starter in driving position; and

Fig. 3 is a plan view of the starting spring device, demounted from a model engine.

Generally speaking, the starter comprises a spring member, one end of which may be securely fastened to a stationary part of the engine, and the free end of which may be secured to the drive shaft. The spring becomes energized when the drive shaft is operated in the contranormal direction, and the spring automatically disengages itself when its energy has been expended during the starting operation.

Looking again to the drawing, the starter comprises a 2 spring 11, preferably formed of music wire, stainless steel, bronze, or other high strength material capable of developing enough energy to rotate the crank shaft through the desired number of rotations. Although various shapes of springs may operate successfully, 'I prefer to use a spirally or helically wound type which is capable of absorbing a substantial amount of energy. The spring 11 is illustrated in connection with a model internal-combustion engine 12 having at least one cylinder 13, and having a piston actuated crank shaft 14 with output connection 15 to which a propeller 16 or other similar power takeoff device is attached. The drive shaft is supported within a tubular journal 17 which also preferably acts as a support or guide for the spring 11.

The torsion spring 11 hence is generally coaxially disposed relative to the shaft and is provided with .one end or terminal that may be connected in some manner to a stationary portion of the engine. In a preferred form the stationary terminal comprises a loop 18, formed about an axis perpendicular to the axis of the coiled spring. The loop 18 preferably is positioned and dimensioned .so as to firmly engage and at least partially encircle the base of the cylinder 13, thus firmly anchoring one end of the spring.

The opposite end of the spring connects with the shaft, and as illustrated may be formed into a hook 19 adapted to be engaged by the propeller or other portion of the drive shaft in such a manner as to cause the turns of'the spring to become constricted and the spring to become energized when the shaft is rotated in a contra-normal direction. Similar results may be obtained, however, with a spring of the opposite lay, whereby the spring becomes energized when the turns are expanded. The spring preferably is made with spaced turns, and of a length requiring the spring to be stretched in order for the hook 19 to engage the propeller 16. The hook accordingly disengages itself automatically from the .propeller when the spring becomes de-energized, as whenthe engine starts and the propeller rotates under its own power. Thus, although the hook may be stretched into engagement with the propeller, as soon as the engine has started the hook retracts so that it in no way interferes with the operation of the propeller.

In operation, the hook 19 is engaged with the base of the propeller 16 as shown in Fig. 2, and the propeller rotated several times in the reverse or clockwise direction, thereby constricting the turns of the spring, and impartingsufilcient energy thereto as .to cause rotation of the propeller in the normal or operating direction (counter-clockwise) as soon as the finger tip is removed. A properly designed spring imparts several complete revolutions to the shaft, efiective in producing quick and reliable engine starting.

On a typical installation in connection with a .054 H. P. motor operative at approximately 15,000 R. P. M., the starting spring comprises approximately 10 turns of .035" music wire with an inside coil diameter of about /2", and weighs approximately ounce.

Although I have herein disclosed a preferred embodiment of the present invention, it is to be understood that the invention is not to be construed in a limiting sense, as I comprehend all modifications properly within the scope of the appended claims.

I claim:

1. A model internal-combustion engine having a piston-operated crank shaft, a stationary journal for said shaft, and a drive-shaft connection projecting from said journal; and a spring starter for said engine comprising a torsion spring encircling said journal, said spring having one end secured to a stationary portion of said engine, and having a free end detachably connected to said drive shaft connection for automatic disengagement from said shaft connection when said spring becomes de-energized.

2. A model internal-combustion engine having a piston-operated crank shaft, a tubular journal for said shaft, and a drive-shaft connectionprojecting from said/journal; and a spring starter for said engine comprising a torsion spring encircling said journal, said spring having one end secured to a stationary portion of said engine, and having a free end formed into a hook engageable with but normally retracted from said drive shaft connection, said engaged connection being operable to energize said spring when said shaft is rotated in a contranormal direction.

3. A model internal-combustion engine having a rotatable shaftdriven by said engine, a propeller secured to said shaft, and a starting mechanism for said engine, comprising a spring member having one end secured to a stationary part of said engine, and having a free end detachably engageable with said shaft for driving said propeller, said shaft being operable to energize said spring when said propeller is rotated in a contra-normal direction.

4. A model internal-combustion engine having a rotatable shaft driven by said engine, a propeller secured to said shaft, and a starting mechanism for said engine, comprising a spring member having one end secured to a stationary part of said engine, and having a free end engageable with said propeller and being operable thereby to energize said spring when said propeller is rotated in a contra-normal direction, said spring being a helically coiled wire, the free end of which includes a hook-shaped terminal operative when said spring is energized to impart several starting turns to said propeller.

5. A model internal-combustion engine having at least one drive cylinder, a rotatable shaft driven by said engine, a propeller secured to said shaft, and a starting mechanism for said engine, comprising a spring member having a stationary end secured to said engine, and having a free end engageable with said propeller and being operable thereby to energize said spring when said propeller is rotated in a contra-normal direction, said spring being a helically coiled wire, the stationary end of which comprises an open coil embracing said cylinder, and the free end of which includes a hook-shaped terminal operative when said spring is energized to impart several starting turns to said propeller, and thereafter to disengage itself from said propeller.

6. A self-starter for a model internal-combustion engine of the type having a source of power, a propeller shaft operated by said source, and a journal for said shaft, said starter comprising a coiled spring for mounting over said journal, said spring having a stationary end formed for attachment to said engine, and having a free end hooked for engagement with said propeller, such that when said propeller is rotated in a contra-normal direction said spring is energized, said spring being short enough as to require stretching to engage said hooked end with propeller, whereby said hooked disengages itself from said propeller when'said spring is de-energized.

7. A self-starter for a model internal-combustion engine of the type having a cylinder, a piston-operated crank shaft, and a propeller connected to said crank shaft, said starter comprising a coil spring adapted to be disposed about a portion of said crank shaft between said cylinder and said propeller, one end of said spring comprising a loop adapted to at least partially encircle said cylinder so as to fasten one end of said spring to said engine, and the other end of said spring comprising a hook adapted when said spring is stretched to engage said propeller, whereby the turns of said spring are constricted and said spring energized when said propeller is rotated in a contra-normal direction.

8. A self-starter accessory for a model internal-combustion engine of the type having a propeller shaft extending from and driven by said engine, said starter comprising a spring member having means at one end engageable with a stationary part of said engine, and having an opposite end for connection with said propeller shaft,

said propeller shaft being operable to energize said spring when said propeller shaft is rotated in a contra-normal direction, said spring when energized being operable to drive said shaft in a normal direction, and to become disengaged from the driving position when said spring is de-energized.

9. A self-starter for a model internal-combustion en- 'gine of the type having a source of power, a propeller,

when said propeller is rotated in a contra-normal direction said spring is energized, and such that when said spring is de-energized said free end automatically disengages.

References Cited in the file of this patent UNITED STATES PATENTS 896,057 Corey Aug. 11, 1908 2,448,844 Throsel Sept. 7, 1948 2,461,784 Streed Feb. 15, 1949 

